Polyurethane elastomers have long been used in coating, adhesive and sealant compositions, and more recently have found utility in specialty applications such as chemical mechanical polishing (CMP) pads.
U.S. Pat. No. 5,965,460, for example, discloses CMP pads produced utilizing UV curable polyurethane materials. However, the pads disclosed suffer from several practical deficiencies. First, the uncured compositions have very high viscosities, between 10,000 cps and 200,000 cps at room temperature, which can lead to difficulties in handling and processing. Second, the Examples illustrate the materials suffer from oxygen inhibition during UV curing, which leads to uncured material on the outer surface of the pads. To mitigate against oxygen inhibition, the pads must either be cured in an inert atmosphere or a cover is placed over the uncured material, to prevent oxygen from reaching the surface of the material. In the event such techniques are not used, uncured material must be removed by conventional techniques, such as a solvent wipe, prior to use of the cured elastomer.
Improved methods for making UV-cured high thickness elastomers are, therefore, desirable.